Automatic centrifuge cleaning system



. Jan. 30, 1968 v T. EASTON 3,366,319

AUTOMATIC CEN'IRIFUGE CLEANING SYSTEM Filed April 7, 1966 s Sheets-Sheet 1 35m Centrifuge L 44 2 41 Advonce Retroct 42 51 48 46 49 55 I 53 It I 32 X Sol.

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-25 Arlyn T. Euston Air Jan. 30, 1968 A. T. EASTON AUTOMATIC CENTRIFUGE CLEANING SYSTEM 5 Sheets-Sheet 3 Filed April 7, 1966 United States Patent 3,366,319 AUTOMATIC CENIRIFUGE CLEANING SYSTEM Arlyn T. Easton, Florence, Ky., assignor to The Cincinnati Milling Machine (10., Cincinnati, Ohio, a corporation of Qhio Filed Apr. 7, 1966, Ser. No. 540,955 Claims. (Cl. 233-19) This invention relates to automatic centrifuge systems and more particularly to a system adapted for separating heavy materials from lighter materials in a fluid mixture wherein the amount or concentration of the heavier material varies from time to time in a random manner.

Centrifuges are sometimes operated in a manual cycle, that is, by a human operator who watches the cycle and decides when the sludge or heavier matter concentration of fluid being skimmed off is high enough that it should be directed away from one destination to another. This system is often used when the input fluid concentration varies in a random manner but it is disadvantageous in that it requires constant operator attention and in that it also requires a judgment which can vary from time to time and from operator to operator.

Centrifuges have also been operated in automatic cycles but these have employed timin devices which operate to direct the fluids being skimmed off to their proper destination in accordance with a preset time schedule. This is a satisfactory method and apparatus for use when the concentration of the supply furnished to the centrifuge is constant but is unsatisfactory when the concentration of supply fluid varies in a random manner.

It is therefore an object of this invention to provide an automatically operated centrifuge system which varies its own cycle to adjust to random variations in the concentration of heavy and lighter weight constituents in the fluid mixture furnished to it.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

The present invention employs a centrifuge having a skimmer that traverses a rotating volume of fluid, the heavier, portions of which are to be separated out. The centrifuge is motor driven and the power supply to this motor is constantly monitored to determine the power re quired to maintain a constant rotational velocity, The skimmer represents a resistance to rotation of the fluid and the resistive force produced by it is directly proportional to the density of the fluid in which it is located at any instant. Therefore, as the skimmer is moved from fluid of one density to another, the resistance to rotation of the fluid mass changes and this is directly reflected in the motor power requirements for the centrifuge motor. An automatic fluid flow directing device is made to operate when a predetermined change in the motor signal is detected and changes the destination of the fluid from the skimmer from one place to another.

A clear understanding of the present invention can be obtained from the following detailed description of a specific embodiment of the invention which is illustrated by the attached drawings wherein:

FIG. 1 is a diagrammatic showing of an electrolyte cleaning and supply system for an electro-chemical machining apparatus where cleaning is performed in a centrifuge apparatus.

FIG. 2 is a schematic showing of a control circuit for the centrifuge portion of the apparatus of FIG. 1.

FIG. 3 is a wiring diagram of a surge switch device used in conjunction with the apparatus of FIG. 1 and circuit of FIG. 2.

FIG. 4 is a partial section view of a simplified centrifuge mechanism of the type employed in the present invention.

In the electro-chemical machining system shown in FIG. 1, clean electrolyte is stored in a supply tank 19 from which it is drawn for use through a pipe 11 by a pump 12. Fluid under pressure is discharged from the pump 12 to a pipe 13 connecting with a pressure reducing valve 14 from which the fluid is passed by way of a pipe 15 to an air piston operated control valve 16. Assuming that a machining operation is taking place, a cylinder 17 of the valve 16 would be under pressure and therefore the pipe 15 is connected as shown to a pipe 18 that carries the fluid to a cartridge type filter 19 and from there, the fluid is supplied to the electro-chemical process machine 26 by a pipe 21. After use in the machine, the fluid, which is now contaminated with swarf, is passed through a gravity drain pipe 22 to a dirty fluid supply tank 23 where the dirty fluid is accumulated prior to centrifuging. Electrochemical machining is an example of a process which generates a variable amount of heavier material in a slurry form since the amount of heavier solids depends upon size or shape of hole being formed, material being eroded and rate of erosion, These vary from job to job and often vary from time to time in any single job.

The connection of air under pressure to the cylinder 17 of the valve 1d and to another cylinder 24 at the opposite end of the valve 16 is controlled by an electrical solenoid operated valve 25. This valve 25 is placed in the condition shown by conventional control circuitry (not shown) to connect air from a supply line 2d to a control line 27 connecting with the cylinder 17. When machining is stopped, the condition of the valve 25 is reversed by the control circuitry and air under pressure is connected from the line 26 to a control line 28 that connects with the cylinder 24 to reverse the position of the valve 16. In this reversed position, the pipe 15 is connected to a restricted pipe 29 that returns the electrolyte directly to the clean fluid supply tank 19 thereby bypassing the machine 2t) and any centrifuging since the clean electrolyte has not been used.

A pump 30, driven by a motor 31 is provided to draw dirty electrolyte from the tank 23 where it is accumulated and to force it through a flow control valve 32 and discharge pipe 33 into a centrifuge mechanism 34. Electrolyte that is thoroughly cleaned and separated in the centrifuge 34 is returned through a gravity return pipe 35 to the clean tank It).

The centrifuge 34 is equipped with a sludge skimmer 36 which is shifted radially in the centrifuge by a pneumatic piston and cylinder motor 37 to scoop up sludge during the centrifuge cleaning cycle. The centrifuge 34 is powered by an electric motor 38 which operates to rotate the mass of fluid within the centrifuge at a constant rotational velocity during this cycle. Fluid which is picked up by the skimmer 36 passes through a flexible hose 39 to a flow control valve 40 which is operable from one to another positions by operation of pneumatic cylinders 41, 42 at opposite ends thereof. When air is connected to the cylinder 41, the valve 40 is in the control condition shown and the hose 39 is connected to a pipe 43 that returns fluid to the dirty fluid tank 23 for recycling through the centrifuge 34. When air is connected to the cylinder 42, the fluid picked up by the skimmer 36 is discharged to a pipe 44 which carries it away as waste to either a sewer or to a Waste receptacle.

The skimmer motor 37 and the control valve 4d in the centrifuge system are pneumatically actuated by air from the main supply line 26. An air line 45 is connected with the line 26 to direct compressed air to a solenoid operated valve 46which connects air through a line 47 to the cylinder 41 when it is held in the position shown by the energization of the solenoid 48. When this solenoid is deenergized and the solenoid 49 is energized, compressed air is connected through a line 50 to the cylinder 42 to reverse the valve 40 from the condition shown.

A second solenoid valve 51 is provided in the centrifuge system to control the operation of the motor 37. Cornpressed air from the line 45 is passed through a line 52 to the valve 51 which is held in the condition shown by a spring 53. Air from the line 52 is connected to a control line 54 that connects to the left end (as viewed in FIG. 1) of the motor 37 to hold the skimmer retracted in the centrifuge 34 where it will not pick up any fluid. When the solenoid 55 is energized, the valve 51 is shifted to connect compressed air from the line 52 to a control line 56 and thus reverses the pressure differential in the motor 37 that eflects a feeding of the skimmer 36 from the retracted position to an advanced position during which the skimmer 36 passes first through relatively clean fluid and then into the heavy sludge. After the arrival of the skimmer 36 at the advanced position, the solenoid 55 is deenergized to cause a return of the valve 51 to the state shown whereby the skimmer motor 37 is reversed and the skimmer 36 is returned through a retraction stroke to its retracted position.

A simplified, typical centrifuge mechanism is shown in FIG. 4 and brief reference to it will assist inthe tmderstanding of the basic centrifuging process. The mechanism includes a stationary tub 58 from which the gravity drain pipe 35 extends. A rotating tub 59 is contained within the stationary tub 58 and is rotated at a relatively high angular velocity by an input drive through a shaft 60. A series of paddle members 61 are spaced around and fixed to the inside of the rotating tub 59 to form pockets therearound which prevent turbulent movement of the fluid therein during a centrifuging process. Dirty fluid is input to the rotating tub 59 from the pipe 33 which directs the fluid first to the inside of a cone member 62 that rotates with the tub 59. The centrifugal forces cause the fluid entering the cone 62 to be moved outward and therefore downward to the bottom of the tub 59 and then radially outward to the periphery. As a result of the feed of new fluid at the bottom of the tub 59, the flow at the periphery of. the tub 59 is upward and at the same time the heavier portions tend to concentrate at the outer edge of the tub 59. The upward migration of fluid causes fluid to be moved against the top 63 of the tub 59 and the less dense portion is forced radially inward to the inside edge 64 of the top, this edge sometimes is termed the curb of the centrifuge, where it is flung outward to the stationary tub and caught. This fluid that escapes from the tub 59 over the curb 64 is the clean fluid and is returned to the clean tank 10 by the pipe 35.

The skimmer 36 is moved radially outward through the fluid which accumulates at the top of the tub 59 above the paddle members 61. Due to the general upward migration of fluid and the centrifugal forces which cause the heavier solids to move radially outward the sludge will tend to be concentrated at the radial extremes of the area in which the skimmer 36 is moved. Therefore in moving radially outward the skimmer will pass through some electrolyte which has a low sludge concentration before engaging the heavy sludge that is to be discharged by way of the waste pipe 44, FIG. 1.

The centrifuging process is operated in a completely automatic cycle, especially in the control of the valves 46 and whereby the material from the skimmer 36 and hose 39 are directed to either the dirty fluid tank 23 or to the waste pipe 44. A source of power 65 is connected across the main power lines 66, 67 to furnish electrical energy for operating the electrical circuit elements. To

start the automatic cycling, :1 start switch 68 is momentarily depressed to connect power through a normally closed stop switch 69 to energize a relay ZCR. The contacts 2CR-1 in parallel with the switch 68 are closed to latch the relay 2CR in its energized state. Another set of contacts ZCR-Z are also closed and power is connected to a motor start relay 3M through normally closed contacts 3CR1 of a control relay 3CR. The motor start relay 3M applies power to the pump motor 31 so that fluid is pumped from the tank 23 to the centrifuge 34. The centrifuge motor 38 has been previously energized by a conventional master start switch (not shown) so that the tub 59 is rotating at this time.

The filling of the centrifuge with dirty electrolyte occurs in a timed cycle controlled by a timer 3TR. The contacts 2CR-3 and 2CR-4 are closed when the cycle control relay ZCR is energized. When the contacts 2CR4 are closed a circuit is completed through the normally closed contacts 3CR-3 of a relay 3CR anda timer clutch winding 70 for the timer 3TR. When the clutch 70 is energized the contacts STR-l are closed and a circuit is completed through these contacts and the contacts 2CR-3 and 3CR2 to cause the timer 3TR to begin its time cycle. During this timed interval, the centrifuge 34 is being filled with dirty electrolyte from the tank 23.

After a preset time, the centrifuge 34 is filled, and the timer times out. The timed operating contacts 3TR-2 are closed and the clutch winding 71 of a second timer 4TR is energized. The energization of the clutch 71 causes two sets of contacts 4TR-1 and 4TR-2 to be closed. The contacts 4TR-2 are in parallel with the contacts 3TR-2 so that the energizing circuit to the timer 4TR is latched to be independent of subsequent operation :of the contacts 3TR2.

When the timer 4TR is energized, the relay 3CR is also energized and its normally closed contacts 3CR-1, 3CR-2, 3CR3 are all opened. Therefore, the pump motor relay 3M is deenergized and the pump motor 31 is stopped. The timer STR is deenergized and the contacts BTR-l are opened since the clutch 70 is also deenergized. This causes the timer 3TR to be reset in preparation for another cycle. The contacts 3TR-2 are also opened when the timer 3TR is reset but the timer 4TR remains energized until it times out since the latch contacts 4TR-2 are.

closed for this period as described.

The function of the timer 4TR is to provide a period of time during which the skimmer 36 is moved from its retracted position to the outward edge of the centrifuge 34. Therefore the relay 3CR which is energized while the timer HR is energized has contacts 3CR-4 and 3CR-5 in series with the solenoid winding 55 that shifts the valve 51 to the condition reversed from that shown in FTG. 1 so that air under pressure is connected to the right side (as viewed in FIG. 1) of the motor 37. This causes the skimmer 34 to be moved toward the outside of the centrifuge.

At this same time, a relay SCR is energized through normally closed contacts of a relay 4CR. Contacts 5CR-1 and 5CR2 are therefore closed and the solenoid 48 is energized to hold the pilot valve 46 in the'position shown and therefore the valve 40 is also in the position shown. The fluid that is first captured by the skimmer 36 is therefore returned to the dirty tank 23. At some time during the skimming cycle, the skimmer 36 encounters the heavier sludge in the centrifuge and the constant speed motor 38 immediately begins to draw more current. An electrical surge switch, to be described in detail later herein, senses this increased current and operates a set of contacts 72 which are closed to energize a'relay 4CR. The relay CR is latched energized through its contacts 4CR2 while the timer TR remains energized. The normally closed contacts 4CR1 are opened at this same time to deenergize the relay 5CR and thereby the solenoid 48 is deenergized. The solenoid 49 is now energized since the contacts 4CR-3 andACR-. are closed with the ener-.

gization or" the relay 4CR. The valve 46 is then shifted from the position shown in PEG. 1 so that air under pressure is connected to the cylinder 42 of the valve 49 which then connects the skimmer hose 39 to the waste line 44. This connection of the skimmer hose 39 to the waste line 44 is then maintained until the timer 4TR times out and the contacts 4TR1, 4TR-2 open to stop the skimmer operation cycle. The contacts 4CR1 are then reclosed and the skimmer 36 is retracted.

The relay 3CR is deenergized at the same time that the relay 4CR is deenergized so that the timer 3TR is again started in its timing cycle b the restoration of the contacts 3CR2, 3CR-3 to their normally closed tate. Thus, the automatic cleaning cycle is begun again. Variations in the amount of sludge introduced into the centrifuge 34 will not, however, change the efficiency since no waste will be discharged until the skimmer 36 actually engages this denser sludge material.

The surge switch is shown in detail in FIG. 3 and is comprised of the contacts 72 which are operated to change from the normally open condition shown to their closed state when a predetermined level of conduction occurs through an electro-magnetic coil 73. The balance of the circuit shown in FIG. 3 is a detection circuit which causes an increased level of conduction in the coil 73 when the load on the centrifuge motor is increased to a predetermined level. One of the conductors of a three phase power source connecting this source to the motor 34 is represented by the line portion 74. A signal pick-up coil 75 is disposed around the line 74 and is connected at one end to the wiper of a potentiometer 77 which has been set at some position to connect a cut-off bias voltage to the control grid of a pentode tube 78. Therefore the tube 78 is conducting at a very low rate and its plate current which passes through the coil 73 is at a low level not suflicient to close the contacts 72. The potentiometer 77 is in a series circuit with a load-resistance 79 and a rectifying diode 80 and the series circuit is connected across a pair of output lines 81, 82 from an alternating current source 83. A capacitor 84 is connected in parallel with the potentiometer 77 to tend to smooth the rectified current therethrough. The wiper 76 is connected to a series circuit including a current limiting resistance 85 and a diode 86 which series circuit is connected, as shown across the coil 75. The diode 86 acts to rectify the signal across the coil 75 and to smooth the resulting half wave signal, a capacitor 89 is provided in series with the input resistance 85.

As an increased signal is picked up by the coil 75, the conduction through the diode 86 increases, the tube resistance decreases and the junction point between the resistance 85 and another resistance 87 goes in a positive voltage direction to raise the grid potential of the pentode 78. This turns on the tube 78 to conduct more heavily and the current reaches a level sufiicient to operate the contacts 72 at some predetermined increased conduction level in the wire 74. The predetermined level required is dependent upon the setting of the potentiometer wiper 76 so that any desired increase in load can be selected as the threshold point at which the relay contacts 72 will be closed. A capacitor 83 is provided in series with the coil 73 to insure that the tendency for pulsating current through the tube 78 will properly operate the relay contacts 72 since the tube 78 is connected to an alternatautomatic centrifuging system is provided which will vary its own cycle of operation to separate heavier matter out in the same efiicient manner even though a mixture is supplied to the centrifuge having a randomly varying percentage of heavier matter therein.

What is claimed is:

1. In a centrifuge system having a rotating member, power means for rotation thereof and a skimmer movable transversely therein between a retracted position and an advanced position to pick up portions of a fluid mass rotating therewith, the combination comprising:

(a) a conduit for carrying fluid away from the skimmer,

(b) a valve in fluid circuit with said conduit and having alternate control states,

(c) a pair of discharge pipes connected to said valve, one and the other ot said discharge pipes placed in communication with said conduit by said valve in one and the other of said control states, respectively, and

(d) means for operating said valve to change the state thereof in response to the passage of said skimmer from fluid of one density to fluid of another density during movement of said skimmer between the retracted and advanced positions thereof.

2. The apparatus of claim 1 wherein said last recited means includes:

(a) means for detecting changes in the energy input to the power means and for producing a signal having a parameter changing in correspondence therewith, and

(b) means for changing the state of said valve in response to said signal when said signal parameter changes by a preset amount.

3. The apparatus of claim 2 wherein:

(a) an electrically operated pilot device is combined with said valve for changing the state thereof,

(b) said signal is electrical, and

(0) means are provided for manipulation of said pilot device when said signal changes in amplitude by a preset amount.

4. The apparatus of claim 1 wherein:

(a) said power means is a constant speed electric motor,

(b) said means for operating the valve includes an electrical surge detection circuit connected to monitor the changes in electrical power input to said motor and a switching device operable by said surge detection circuit to change the state of said valve when a predetermined change occurs in the power input to said motor.

5. The apparatus of claim 4 wherein:

(a) means are provided for presetting the surge detection circuit to operate said switching device when a selected change occurs in the power input to said motor.

References Cited UNITED STATES PATENTS 2,961,154 11/1960 Bergey 23319 3,070,291 12/1962 Bergey 233---19 3,141,846 7/1964 Laven 23319 FOREIGN PATENTS 915,076 7/1949 Germany.

HENRY T. KLINKSIEK, Primary Examiner. 

1. IN A CENTRIFUGE SYSTEM HAVING A ROTATING MEMBER, POWER MEANS FOR ROTATION THEREOF AND A SKIMMER MOVABLE TRANSVERSELY THEREIN BETWEEN A RETRACTED POSITION AND AN ADVANCED POSITION TO PICK UP PORTIONS OF A FLUID MEANS ROTATING THEREWITH, THE COMBINATION COMPRISING: (A) A CONDUIT FOR CARRYING FLUID AWAY FROM THE SKIMMER, (B) A VALVE IN FLUID CIRCUIT WITH SAID CONDUIT AND HAVING ALTERNATE CONTROL STATES, (C) A PAIR OF DISCHARGE PIPES CONNECTED TO SAID VALVE, ONE AND THE OTHER OF SAID DISCHARGE PIPES PLACED IN COMMUNICATION WITH SAID CONDUIT BY SAID VALVE IN ONE AND THE OTHER OF SAID CONTROL STATES, RESPECTIVELY AND (D) MEANS FOR OPERATING SAID VALVE TO CHANGE THE STATE THEREOF IN RESPONSE TO THE PASSAGE OF SAID SKIMMER FROM FLUID OF ONE DENSITY TO FLUID OF ANOTHER DENSITY DURING MOVEMENT OF SAID SKIMMER BETWEEN THE RETRACTED AND ADVANCED POSITIONS THEREOF. 